Host diversity and landscape structure drive genospecies-specific Lyme disease risk across Eurasia

Lyme disease, caused by Borrelia burgdorferi sensu lato (s.l.), is the most prevalent tick-borne disease in the Northern Hemisphere, posing an escalating global health challenge driven by climate change and land-use transformation. However, mechanistic understanding of how environmental factors govern genospecies-specific transmission remains limited.

We compiled the first comprehensive Eurasian dataset of B. burgdorferi s.l. prevalence, comprising 2,528 records from 522 publications across 43 countries (2000–2023). The dataset encompasses 73 tick species from 6 genera and documents 18 Borrelia genospecies. We applied causal-pathway modeling to disentangle direct, indirect, and cascading effects of climate, land cover, landscape structure, and host biodiversity on pathogen prevalence, with host diversity taxonomically stratified according to genospecies-specific reservoir ecology.

Our results reveal distinct biogeographic patterns shaped by vector-host specificity. Ixodes ricinus dominates transmission in Europe while I. persulcatus prevails in Asia. B. afzelii predominates in Central and Western Europe, whereas B. garinii exhibits transcontinental distribution from Western Europe through Russia to East Asia. Critically, B. afzelii prevalence was co-regulated by climate, forest fragmentation, and landscape diversity, and declined significantly with increasing rodent species richness. This provides the first continental-scale empirical support for the dilution effect hypothesis in Eurasia. Forest fragmentation showed opposing pathways: directly amplifying prevalence through edge effects while indirectly suppressing transmission by enhancing host diversity. In contrast, B. garinii showed no detectable host diversity effects but responded directly to temperature and landscape diversity, reflecting reliance on highly mobile avian hosts whose infection status integrates exposure across multiple migratory stopover sites.

These findings reveal fundamental transmission heterogeneity among genospecies with critical implications for disease surveillance and control. Effective management must integrate genospecies-specific ecology with landscape management, unifying biodiversity conservation, climate adaptation, and planetary health protection.